go to sleep/fall asleep/be asleep

fall asleep 常常强调本不想睡却睡着了,相当于 drop asleep。例如:

1. He fell asleep during the sermon. (ALD) 他在布道时睡着了。

2. She was falling asleep when he came in. 他进来时她正要入睡。

be asleep 与 fall asleep 的区别: 前者表示状态, 后者表示动作。

He seems to be fast asleep. (Bennet) 他似乎在熟睡。